It's not exactly shocking news but it's still a bummer to hear.
Here's the statement from the team:
"After a recent MRI with dye contrast was performed on Mark Teixeira’s right wrist. New York Yankees Team Physician, Dr. Christopher Ahmad, along with Dr. Melvin Rosenwasser and two other New York-based hand specialists (Dr. Michelle Carlson from the Hospital for Special Surgery and Dr. Keith Raskin from NYU) confirmed that the sheath has not adequately healed. Surgery has been recommended to repair the tear on the tendon sheath of his wrist."
It is likely that Teixeira will miss the rest of the season.